Radio-frequency identification (RFID) is a ubiquitous technology that employs electromagnetic fields to automatically identify and track tags that contain electronically stored information. Passive RFID tags collect energy from a nearby RFID reader's interrogating radio-frequency (RF) signal to report the electronic data stored within the tag. The data may include a unique electronic product code (EPC) that can be associated with the characteristics of the object to which the tag is connected.
Because RFID tags use radio-frequency (RF) signals, they need not be within the line of sight of the RFID reader, an advantage over optical barcode technology. RFID tags may thus be embedded in the tracked object or object packaging.
RFID tags are used throughout many industries, including retail, equipment manufacturing, and equipment rental facilities, to name a few. For example, a manufacturing plant may embed an RFID tag on a component, and can track that component throughout the manufacturing process, and the distribution and sale process thereafter. Banks use RFID tags attached to cash to track the flow of money, and such tags are incorporated into the uniform product code (UPC) labels on clothing. Ranchers may implant RFID tags into their animals to track the movement of their herds.
RFID may also be used as part of an inventory management system. A reader may send out an interrogation RF signal. Then, for each tag that reports back, the system can flag the associated item as remaining in inventory. Those tags that do not report back are flagged as not in inventory.
When several RFID tags are located within a confined volume, it can be difficult or impossible to interrogate them all. For example, a warehouse may have thousands of tagged items, some of which may be on the fringe of the RFID reading area, while others may be blocked from the interrogating RF signal, preventing their successful interrogation by the RFID reader. Conventional RFID inventory technology will incorrectly flag these non-interrogated tags (and their associated objects) as not in inventory. This false reporting leads to costly lost sales, over-ordering, and over-stocking, frustrating the purposes of RFID inventory management. Accordingly, improvements to existing RFID systems are needed to more accurately detect and report tagged inventory.